A vaporizer of the above type is disclosed in U.S. Pat No. 4,017,566. The vaporizer vaporizes a liquid anesthetic which is contained in an appropriate vessel through which a component flow of a carrier gas is conducted. The carrier gas can, for example, be oxygen which is saturated with the anesthetic vaporized via a wick. The component flow of the carrier gas which is free of anesthetic is again conducted to the component flow containing anesthetic via a bypass line connected in parallel to the input and the output of the vaporizer. This gas mixture is conducted to a user for breathing who in the familiar situation is a patient. The concentration of the gas mixture which is formed is determined by means of the adjustable proportion of the through-flow of the vaporizer and the bypass line.
The vaporized quantity of a liquid is dependent from several parameters such as the temperature of the liquid. For this reason, an appropriate arrangement is provided for the known vaporizer for compensating for this temperature influence on the vaporized quantity. Other external parameters not influenceable by the user of the vaporizer, however, as before, lead to undesired fluctuations of the quantity of vapor given off.
The adjustment of the component flows through the vaporizer and through the bypass line are adjusted in the known vaporizer by means of an adjustable flow resistance which is dependent upon the flow velocity. In addition, fluctuations in pressure at the output of the vaporizer can lead to flow fluctuations in the vaporizer itself and thereby lead to fluctuations in the vaporization quantity delivered to the carrier gas. Also, when there are changes in the type of carrier gas, the flow relationships in the flow resistances change and lead to a varying division of the component flows through the vaporizer and through the bypass line.
Since a large range of application of the known vaporizer for vaporizing volatile anesthetic mediums with a high partial pressure serves for assisted or mandatory ventilation of anesthetized patients and because a most precise and fluctuation-free metering of the anesthetic is required for this application, the above-mentioned external influences on the vaporizer are considerable and lead to undesired fluctuations in the concentration of the anesthetic in the carrier gas.